Process for Removing Sulphur Dioxide from a Gas

摘要

1,160,197. Removing sulphur dioxide from gases. LUMMUS CO. 23 April, 1968 [24 April. 1967], No. 19188/68. Heading C1A. Sulphur dioxide is removed from a gas by contacting the gas with a metal carbonate to produce a metal sulphite, the carbonate being regenerated by reacting the metal sulphite with carbon monoxide to give the carbonate, carbon dioxide and sulphur. In the described process (see Figure) a gas containing SO 2 is passed via 10 into absorber 11 charged with an alkalimetal or alkaline-earth metal or zinc carbonate at 250-1000‹ F., the purified gas being passed out via 26. After a period of time absorption of SO 2 in 11 is stopped, and the gas instead passed into a similar absorber 12. The absorbent in 11 is then regenerated at 1000-1800‹ F. with carbon monoxide to give carbonate, sulphur and carbon dioxide. The gaseous sulphur is condensed in 30 and 34, while the CO 2 is reduced to CO by a carbonaceous material, such as coke, in 37 and may be reused in the regeneration. Any SO 3 in the SO 2 - containing gas is removed in the process by reaction with the carbonate to a metal sulphate, but reduction with CO reduces the sulphate only to a metal sulphide. Thus additional metal carbonate has to be added to 11 and 12 at intervals. The process is run so that while 11 is absorbing, the material in 12 is regenerated and vice versa. The difference in temperature between 11 and 12 means that after absorption the material in a reactor must be heated, for example, by a hot gas, and after regeneration the material must be cooled, for example by a blast of cold air.